President Donald Trump signed his package of tax breaks and spending cuts into law Friday in front of Fourth of July picnickers after receiving almost unanimous Republican support in Congress for the domestic priority that could cement his second-term legacy.

In a speech from the White House balcony facing the South Lawn, Trump thanked Republican lawmakers who helped usher the bill to his desk. He touted the tax cuts in the bill, brushing aside criticism of the impact to social programmes such as food assistance and Medicaid.

The "big, beautiful bill" will add trillions to the national debt through tax cuts, and millions of people could lose their health insurance.